package a297.二叉树的序列化与反序列化;

public class TreeNode {
 int val;
 TreeNode left;
 TreeNode right;
 TreeNode() {}
 TreeNode(int val) { this.val = val; }
 TreeNode(int val, TreeNode left, TreeNode right) {
  this.val = val;
  this.left = left;
  this.right = right;
 }
}